1. Field of the Invention
The present invention relates to connector blocks used in the multiple circuit modules of electronic devices such as high-speed digital computers of the type produced by Cray Research, the assignee hereof. Specifically, the present invention relates to shielded metallic connector blocks for multiple circuit modules which provide completely shielded connector paths between circuit boards.
2. Description of the Prior Art
Circuit boards are utilized in many types of electronic equipment and it is often necessary, particularly in complex equipment, to interconnect the circuit boards into a module, and to interconnect modules into multiple circuit modules. For example, some high-speed electronic digital computers of the type produced by Cray Research utilize circuit modules consisting of four circuit boards mounted in close proximity on opposite sides of two cooling plates. Such circuit modules are arranged in banks and it is, therefore, desirable to interconnect adjacent circuit boards within a module in a manner which permits convenient disconnection for service and reconnection after service, and which also permits reversed stacking for testing.
One previously known example of an interconnected multiple circuit module is disclosed in U.S. Pat. No. 4,514,784 to Williams et al. In this apparatus, conductive pins are used to transmit signals from one circuit module to another. Electrical connection between the pins is accomplished by connector blocks positioned between the modules having bores defined therein for receiving the pins. This type of module connection was a great improvement over previous designs because it minimized twisting and misalignment of the connector elements, while facilitating connection over the shortest circuit paths.
However, as the architecture of high-speed electronic digital computers evolves, greater switching speed and circuit density are required. As circuit density increases, a greater number of connections are necessary between modules, thereby increasing the total force needed to connect the modules.
In response to that need, U.S. Pat. No. 4,939,624 to August et al. disclosed an improved interconnected circuit module using connector blocks both between modules and circuit boards within the modules to decrease the total force needed to connect modules while providing an increased number of connections.
As a result of the increased number of connections in the limited space, it became increasingly likely that transmission of a signal through a first circuit path would possibly affect the operation of an adjacent path. This phenomenon is known as cross-talk, and is a major impediment to improved circuit density in high-speed digital computers. The cross-talk problem has two components, capacitive cross-talk and inductive cross-talk. U.S. Pat. No. 4,939,624 attempted to solve that problem by incorporating additional shielding elements in or on the blocks. Such an approach, however, effectively dealt only with capacitive cross-talk and failed with respect to inductive cross-talk. In addition, it added significantly to the cost and complexity of the connector blocks.
It is clear that there has existed an unfilled need for improved connector blocks for use in interconnected multiple circuit modules which reduce the aggregate force necessary for assembly and disassembly while providing adequate shielding to reduce inductive interference between adjacent circuit paths.